Hi everyone,

Please to inform that I manage to make everything run. No more
burning MOSFET, diodes, etc. I think it would be most appropriate to
share it with everyone. The new schematic can be found at the link
below (as usual):

http://f1.grp.yahoofs.com/v1/UG41SHcmGChYa-
2fQRKl2OlPVYWLMhrHHEsJ9bcqHu6XaELlpHrNqPCcl5MzLxialF2iBKK_e1N0BdJiN_AY6Be42v-
R/Sketches/schematic.GIF

What rectifies all of the issues can be found in the schematic,
namely the use of shift level transistor, voltage dividing resistor
(in series), rewiring of the low side MOSFET gate and also add a 10
nF ceramic capacitor across the motor leads (to reduce noise as well
as voltage spike).

To Don, thanks a bunch. Definately will be still searching in the
dark without your enlightenment.

Regards.
--- In b..., "hmwong76" wrote:
>
> Hi Don,
>
> Manage to rewire my whole setup with the 2N3904 transistors and
> voltage dividing series resistors. I think I have found another
> problem.
>
> Seems that on the same side of the motor, the MOSFETs are turned
on.
> As of giving the direction signal LO (pin 2) and PWM HI (pin 5 and
8)
> would yield output of pin 13 (High MOSFET left) HI , pin 12 (High
> MOSFET right) LO, pin 11 (Low MOSFET left) HI and pin 10 (Low
MOSFET
> right) LO. If they were using the same voltage of the motor and the
> TC4469 and turning off and on the MOSFETs, it would yield High side
> right MOSFET on (P channel) and Low side left MOSFET on (N channel).
>
> However, once start using the transistors, HI from pin 13 and 12
> means pulling the series resistors to the ground, thus making the
> MOSFET gate registering 12V from the original 24V. This would means
> switching on the MOSFET. Somehow it inverts the overall intention.
>
> I had checked my wiring of TC4469, going back to the original setup
> connecting pin 13 with pin 4 and 9 while in 12 connect with pin 6.
>
> I think I need to rewire the overall setup to prevent the MOSFETs
> turned on, on the same side.
>
> Regards.
> --- In b..., "Don LeRoi" wrote:
> >
> > --- In b..., "hmwong76" wrote:
> > >
> > > Hi Don,
> > >
> > > Thanks for your pointing me to the correct direction. Looking
at
> > your
> > > schematics, switching off the MOSFET will be having the gate
pull
> > to
> > > 24V. Switching on the MOSFET, using pin 13 of TC4469 to on the
> > > transistor so that the gate will then be pulled towards the
> ground.
> > I
> > > think it will work just that I concern of it being 0V. Can I
add
> > > another resistor between the transistor to ground of more than
> 10k
> > to
> > > raise the gate voltage higher than 12V. This is to have Vgs is -
> 12V
> > > and above. Afraid if pulled straight to ground, then Vgs is -
24V,
> > > more than rated -20V Vgs in the spec of IRF4905. Or is it I
read
> > > wrongly?
> > >
> > > Thanks.
> > >
> > > Regards.
> > >
> >
> > HM,
> >
> > If Vgs is a problem, you might replace the 10K pullup resistor
with
> 2
> > resistors in series to divide the voltage.
> >
> > - Don
>

--- In b..., "hmwong76" wrote:
>
> Don, you are my saviour. Will get the components ASAP as it's a 3 day
> holiday here, have to wait till tomorrow. Will post the latest of my
> adventure. Hope everything will be alright.
>
> Regards.
>

HM,

Hmmm... I hope the suggestions turn out to warrant that!

Did you notice that with the transistors added for level shifting, the
logic goes back to what you had originally posted? That is - pin 13 of
the TC4469 is tied to pins 4&6 and pin 12 is tied to pin 9.

Good luck!

- Don

Hi Don,

Manage to rewire my whole setup with the 2N3904 transistors and
voltage dividing series resistors. I think I have found another
problem.

Seems that on the same side of the motor, the MOSFETs are turned on.
As of giving the direction signal LO (pin 2) and PWM HI (pin 5 and 8)
would yield output of pin 13 (High MOSFET left) HI , pin 12 (High
MOSFET right) LO, pin 11 (Low MOSFET left) HI and pin 10 (Low MOSFET
right) LO. If they were using the same voltage of the motor and the
TC4469 and turning off and on the MOSFETs, it would yield High side
right MOSFET on (P channel) and Low side left MOSFET on (N channel).

However, once start using the transistors, HI from pin 13 and 12
means pulling the series resistors to the ground, thus making the
MOSFET gate registering 12V from the original 24V. This would means
switching on the MOSFET. Somehow it inverts the overall intention.

I had checked my wiring of TC4469, going back to the original setup
connecting pin 13 with pin 4 and 9 while in 12 connect with pin 6.

I think I need to rewire the overall setup to prevent the MOSFETs
turned on, on the same side.

Regards.
--- In b..., "Don LeRoi" wrote:
>
> --- In b..., "hmwong76" wrote:
> >
> > Hi Don,
> >
> > Thanks for your pointing me to the correct direction. Looking at
> your
> > schematics, switching off the MOSFET will be having the gate pull
> to
> > 24V. Switching on the MOSFET, using pin 13 of TC4469 to on the
> > transistor so that the gate will then be pulled towards the
ground.
> I
> > think it will work just that I concern of it being 0V. Can I add
> > another resistor between the transistor to ground of more than
10k
> to
> > raise the gate voltage higher than 12V. This is to have Vgs is -
12V
> > and above. Afraid if pulled straight to ground, then Vgs is -24V,
> > more than rated -20V Vgs in the spec of IRF4905. Or is it I read
> > wrongly?
> >
> > Thanks.
> >
> > Regards.
> > HM,
>
> If Vgs is a problem, you might replace the 10K pullup resistor with
2
> resistors in series to divide the voltage.
>
> - Don
>

Don, you are my saviour. Will get the components ASAP as it's a 3 day
holiday here, have to wait till tomorrow. Will post the latest of my
adventure. Hope everything will be alright.

Regards.
--- In b..., "Don LeRoi" wrote:
>
> --- In b..., "hmwong76" wrote:
> >
> > Hi Don,
> >
> > Thanks for your pointing me to the correct direction. Looking at
> your
> > schematics, switching off the MOSFET will be having the gate pull
> to
> > 24V. Switching on the MOSFET, using pin 13 of TC4469 to on the
> > transistor so that the gate will then be pulled towards the
ground.
> I
> > think it will work just that I concern of it being 0V. Can I add
> > another resistor between the transistor to ground of more than
10k
> to
> > raise the gate voltage higher than 12V. This is to have Vgs is -
12V
> > and above. Afraid if pulled straight to ground, then Vgs is -24V,
> > more than rated -20V Vgs in the spec of IRF4905. Or is it I read
> > wrongly?
> >
> > Thanks.
> >
> > Regards.
> > HM,
>
> If Vgs is a problem, you might replace the 10K pullup resistor with
2
> resistors in series to divide the voltage.
>
> - Don
>

--- In b..., "hmwong76" wrote:
>
> Hi Don,
>
> Thanks for your pointing me to the correct direction. Looking at
your
> schematics, switching off the MOSFET will be having the gate pull
to
> 24V. Switching on the MOSFET, using pin 13 of TC4469 to on the
> transistor so that the gate will then be pulled towards the ground.
I
> think it will work just that I concern of it being 0V. Can I add
> another resistor between the transistor to ground of more than 10k
to
> raise the gate voltage higher than 12V. This is to have Vgs is -12V
> and above. Afraid if pulled straight to ground, then Vgs is -24V,
> more than rated -20V Vgs in the spec of IRF4905. Or is it I read
> wrongly?
>
> Thanks.
>
> Regards.
>

HM,

If Vgs is a problem, you might replace the 10K pullup resistor with 2
resistors in series to divide the voltage.

- Don

Hi Don,

Thanks for your pointing me to the correct direction. Looking at your
schematics, switching off the MOSFET will be having the gate pull to
24V. Switching on the MOSFET, using pin 13 of TC4469 to on the
transistor so that the gate will then be pulled towards the ground. I
think it will work just that I concern of it being 0V. Can I add
another resistor between the transistor to ground of more than 10k to
raise the gate voltage higher than 12V. This is to have Vgs is -12V
and above. Afraid if pulled straight to ground, then Vgs is -24V,
more than rated -20V Vgs in the spec of IRF4905. Or is it I read
wrongly?

Thanks.

Regards.
--- In b..., "Don LeRoi" wrote:
>
> --- In b..., "hmwong76" wrote:
> >
> > Hi Don. The way you put it, you are correct. Seems i
> > made a silly mistake then. Realizing this flaw, came
> > another question. I'm running with 24V, wouldn't at
> > whatever 12 or 0V at the high gate, the P MOSFET
> > would still be on?
> >
> > Regards.
> >
> >
> HM,
>
> Check out the schematic I put in the files section below yours for
a
> possible solution.
>
> - Don
>

--- In b..., "hmwong76" wrote:
>
> Hi Don. The way you put it, you are correct. Seems i
> made a silly mistake then. Realizing this flaw, came
> another question. I'm running with 24V, wouldn't at
> whatever 12 or 0V at the high gate, the P MOSFET
> would still be on?
>
> Regards.
HM,

Check out the schematic I put in the files section below yours for a
possible solution.

- Don

--- In b..., "hmwong76" wrote:
>
> Hi Don. The way you put it, you are correct. Seems i
> made a silly mistake then. Realizing this flaw, came
> another question. I'm running with 24V, wouldn't at
> whatever 12 or 0V at the high gate, the P MOSFET
> would still be on?
>

HM,

I hadn't noticed that. Yes, the P-channel MOSFETs would always be on.
To run on 24V, you will need to do some level shifting in order to turn
the P-channel devices off.

- Don

Hi Don. The way you put it, you are correct. Seems i
made a silly mistake then. Realizing this flaw, came
another question. I'm running with 24V, wouldn't at
whatever 12 or 0V at the high gate, the P MOSFET
would still be on?

Regards.
--- In b..., "Don LeRoi"
..> wrote:
>
> HM,
>
> As I said before, I use the LMD18200 for these
circuits, so I'm not
> very familiar with the discrete H-bridge circuits.
However, I believe
> that your circuit requires a low to turn on the
p-channel mosfets and a
> high to turn on the n-channel mosfets. The way
you have the TC4469
> wired appears to turn on the mosfets that are
directly in series with
> each other, rather than the ones that are on
either side of the motor.
>
> I think that pin 13 of the TC4469 should connect
to pins 4 and 9 and
> pin 12 should connect to pin 6 to get the right
logic.
>
> - Don
>